1973 Johnson 65hp Problems

[wannagetrdone]

Ok I have a 1973 65hp Johnson. My problem is the motor runs on the muffs but wont run in the water. I checked compression and top cyl was 130 sec cyl was 130 bot was 117. I cleaned and kitted the carbs and new plugs etc and still nothing in the water. So I took it to my local boat shop and had them look at it. They called me back and said it was low on compression and thats whats causing it not to run in the water. Does this seem right? He aslo quoted me $1800 to fix. So does anyone have any advice on this. Maybe what compression is suppose to be from the factory?

 

[boobie]

Re: 1973 Johnson 65hp Problems

There are no specs on compression. You don't want over 10 % varieation between the cyls. The shop may be right. Probs on the bottom cyl. A good decarbing with Seaform may help it to free up the rings.

 

[wannagetrdone]

Re: 1973 Johnson 65hp Problems

Well compression in my opinion wasn't bad I didn't think. But I looked at it this weekend and the shop had the head off and you could move the pistons side to side probably 1/8in one direction probably 3/16-1/4in all tigether

 

[boobie]

Re: 1973 Johnson 65hp Problems

Are all the pistons like that or just the cyl with the 117 psi on the compression test ??

 

[wannagetrdone]

Re: 1973 Johnson 65hp Problems

All of them have that much slack.

 

[boobie]

Re: 1973 Johnson 65hp Problems

Did you ever try a GOOD decarb on it ??

 

[wannagetrdone]

Re: 1973 Johnson 65hp Problems

No I never decarbed it. I intend on doing that when I get the motor back Im gonna try to get it running again Im gonna have to buy new gaskets for it anyway now since its in pieces. figured Id try to clean the rings and stuff from the exhaust side cover. If that dont work Ill eventually try my first outboard rebuild. I Know that some slack between the piston and cylinder is normal but do you think that much is?

 

[Aussie Rob]

Re: 1973 Johnson 65hp Problems

Did you ever get to the bottom of this?
I've found it was more of a timing issue and it had to be done on the water. take a timing light and set the idle at 16 degress or as the book states put it into reverse and it should be at 650RPM. the rest is all about link configuration.

I have posted some photos on mine as it is - but it still needs work.

Fishnet | Forums

 

[emdsapmgr]

Re: 1973 Johnson 65hp Problems

That engine may seem to run just fine on the trailer, when firing 2 of the 3 cyls. You may not have fire to all 3 cyls when the boat is floating normally in the lake and fully warmed up. An inductive timing light will show you the firing from all 3 cyls, strong spark, weak spark, intermittents, etc. It's normal to have a lot of piston slop on those 2 strokes. I'd be inclined to do the decarb that boobie has been recommended. Then take another compression reading.It certainly won't hurt.